KVN and VERA Array

KaVA Observing Preparation

General Information

For the accepted proposals, users are requested to prepare the observing schedule file, at least one week before the observation. The observer who is not familiar with KaVA system is recommended to consult with KaVA user support team (kavahelp@kasi.re.kr) to prepare schedules. KaVA operation & support members take full responsibility for observation and correlation process.

Observation

The users are asked to submit a VEX file two weeks before the observation to kavaobs@kasi.re.kr. Observations will be performed by KaVA operators so that users will not be asked to take part in observations.

Correlation

The correlation process will be carried out by Daejeon correlator at KJCC (Korea-Japan Correlation Center). The correlated data can be downloadable via FTP and its address will be given to the PI via email. Then, users are asked to examine the correlated data and if there is some problem, you can request re-correlation within a month after the correlation. In this case, you should provide the details of your problem clearly. In principle, the raw data used for observations will be recycled one month after the correlation.

Data Rights and Archiving

The PIs will have exclusive access to the data obtained for 18 months after the correlation. This policy is applied to each observation, even if the proposal comprises multi epoch observations. After this exclusive period, the data will be publicly accessible.

Schedule Preparation

1. VEX Preparation

You can download the KaVA VEX example file from here and modify them for your observation. The schedule submission should be done by a standalone vex file including calibration procedures (e.g. sky dipping, hot/cold calibration, focusing, pointing etc.). The correlation parameters must be clearly specified as an example VEX file.

2. Frequency Setup (DAS setup)

At present, following observing modes are available. Please refer to the KaVA status report for more details.

  • Frequency band: K (22GHz), Q (43GHz) bands (both in LHCP only)
  • Recording mode: 1024 Mbps (Mark5B for KVN, DIR2000/OCTADISK for VERA)
  • Filtering mode: 16MHz bandwidth x 16 channels

3. Check List of Scheduling

Following items are the check list for the success of VLBI observation.

  • Fringe Finder
    • Good fringe finders are essential to remove large delay errors between the real observation and the correlation model. At least two fringe finder scans must be scheduled at the beginning and the end of your observation with the scan length of 5 minutes for a successful fringe search. It is highly recommended to observe fringe finder sources every 1~2 hours.
    • You must specify the fringe finder sources and correlation parameters on your VEX files explicitly. Please refer to the VEX template for details.
    • Compact and strong source are suitable for fringe finders with well-known source positions at your observing frequency. If your target sources are quite strong, you may not need to observe a fringe finder. Following sources are recommended.
      • 22GHz (> 2Jy): NRAO150, 0420-014, 4C39.25, 3C273, 3C279, NRAO530, 2145+067, 3C454.3, 3C84
      • 43GHz (> 4Jy): NRAO150, 3C279, 3C345

        Source-Elevation plot of several fringe finders


  • Tsys measurements and Pointing correction
    • Tsys measurements for each KaVA antenna is performed by R-Sky method. Hot load is inserted on the front of the feed-horn for 30 seconds before or after each scan (no Tsys measurements during scans). You need to split a consecutive integration into multiple short scans if you would like to track the time variation of Tsys.
    • It is recommanded to perform a pointing correction every hour for KVN antennas. Please insert 2 minutes gap for it. Five pointing for spectral line sources and cross-scan for continuum sources correction are applied.

KASI logo image

KaVA ( KVN and VERA Array )